Question

One half of a lens is covered with a black paper.
(a) Will this lens produce a complete image of an object?
(b) Is there any change in the intensity of the image?
(c) Draw a diagram to show the formation of the image by this lens.
(d) What will happen if we remove the black paper?
[5 MARKS]

Answer 1

part(a),part(b) and part(d): 1 Mark each
part(c): 2 Marks

(a) The lens will form a complete image of the object. As we can see from the ray diagram below, the image of the whole object is formed.
(b) The intensity of the image will decrease. Since the lower part of the lens is covered less number of rays will be able to pass through the lens. So the intensity of the image formed decreases.
(c) The required diagram is shown below.

(d) When the black paper will be removed the intensity of the image formed increases, as more light will be able to pass through the lens.